The Acheron River (アケローン の 河 (アケローン の か わ) (Akeron no kawa)) is the first of four rivers of the Underworld, and acts as the physical border between the Underworld and the world of the living. Its name roughly translates to the River of Lament. Souls destined for the Underworld gather on the shore, where they are ferried to the other side by the boatman and Specter Acheron Charon. To gain passage on the boat, souls must pay a coin to Charon, provided for them by their mourners. Those who were never given a coin cannot get on the boat, and are at risk of wandering back into the land of the living to torture and haunt people as vengeance for not seeing to their eternal rest properly. 

This river was also the site of the battle between Acheron Charon and Pegasus Seiya, when the Bronze Saints descended into the Underworld.